When windows are being replaced, the usual procedure is first to remove the old window from the masonry wall by the use of, for example, a suitable window joint saw. Both the interior plastering and the exterior rendering are separated from the old window frame along a straight, sharply defined line and the old window frame is then taken out. As a result, the old window which has been removed leaves behind, on all sides, a channel-shaped recess between the interior plastering and the exterior rendering. This recess extends all the way to the rough masonry and can even penetrate into it. Such recesses vary in depth and are usually 10-100 mm deep.
Modern window frames are usually wider than old window frames, which means that, when a new window is being installed, the window frame cannot be inserted into the recess but rather must remain outside it. The recess extending all the way around must be filled with a sealing and insulating material, so that, after the new window has been installed, the space between the bottom of the recess and the new window frame is sealed in a manner consistent with good building insulation as defined by the generally recognized rules of the technology.
Injected polyurethane foams or mineral fiber insulating materials, for example, have been used in the past to seal these recesses. Sealing tapes of flexible foam are also used.
In the case of the latter option, flexible foam sealing tapes are attached directly to the new window frame. For example, a window frame equipped with a flexible foam sealing tape is known from US 2011/0185661 A1. The sealing tape can be held in place between the opposing angled edges of two molding profile strips on the window frame. This is done by introducing the stiff layer, on which the flexible foam is mounted, into the intermediate space between the molding profile strips, where it is prevented from slipping out of position by the angled edges. The stiff layer is then destroyed to release the foam, which can finally expand and seal the window frame in the direction toward the masonry. In the case of the previously mentioned process of window replacement, however, it is very difficult to reach the stiff layer after the new window frame has been brought into the desired installation position, and it is also impossible to see whether or not the recess has been sealed completely with the flexible foam strip.
According to US 2011/0143122 A1 and US 2011/0302873 A1, the sealing tape again comprises a layer of flexible foam and a stiff layer. Here, the stiff layer does not have to be destroyed to release the flexible foam, and the flexible foam is arranged on the side of the stiff layer facing the masonry. The stiff layer can be premounted in profiled channels in the window frame by the use of various fastening mechanisms. However, it is still impossible to see whether or not the recess has been sealed completely with the flexible foam strip.
In summary, the combination of a window frame with a sealing tape already premounted on it is not optimally suitable for the window replacement process described above.